1. Field of the Invention
The invention relates to an electromechanical wheel brake device for a motor vehicle, including a helical gear driven by an electric motor for applying and releasing the brakes.
2. Description of the Prior Art
A wheel brake device is already known (DE 197 50 273 A1), in which a threaded spindle, which is part of a planetary roller screw drive and can be moved in the longitudinal direction by a nut driven to rotate by an electric motor, is used to press a brake pad against a brake disc. The threaded spindle is comprised of two parts that axially interlock in a positively engaging manner. During normal operation of the wheel brake device, an inner part of the threaded spindle is kept axially and rotationally stationary by an electromagnetically actuat d clutch; an outer part is guided on the inner part in a longitudinally mobile fashion. To avoid damage to the wheel brake device in the event of an incorrect continuous supply of power to the electric motor in the restoring stroke of the outer threaded spindle part, the clutch can also be mechanically switched by this part of the threaded spindle. As a result, the threaded spindle can rotate freely and is operatively disengaged from the electric motor.